1. Technical Field
The present invention relates to a battery monitoring apparatus for monitoring a battery condition of an assembled battery formed of a plurality of battery cells connected in series.
2. Related Art
A known battery monitoring apparatus includes, as main components, a monitoring unit that monitors a battery condition, such as an over-charge or over-discharge condition, of each of a plurality of battery cells forming an assembled battery, and a control unit that controls the operation of the monitoring unit.
The monitoring unit of the battery monitoring apparatus is powered by the assembled battery that is a monitored object. Therefore, the consumption of power by the monitoring circuit will lead to a reduction in state of charge (SOC) of each battery cell of the assembled battery. In addition, when the monitoring unit operates unnecessarily, the power consumed by the monitoring unit is increased, which facilitates a reduction in SOC of the assembled battery. This may lead to an over-discharge condition of each battery cell of the assembled battery.
To reduce the power consumed by the monitoring unit, there has been proposed a battery monitoring apparatus as disclosed in Japanese Patent No. 4114310 including a dark-current mode (or a sleep mode) in which power supply from the assembled battery to the monitoring unit is limited when a prescribed condition is met. The disclosed battery monitoring apparatus is configured such that the monitoring unit transitions to the dark-current mode when the control unit is receiving no monitoring results (in the form of monitoring information signals) from the monitoring unit.
In the disclosed battery monitoring apparatus, however, the control unit is unable to diagnose whether or not the dark-current mode of the monitoring unit is functioning normally. Accordingly, when the dark-current mode of the monitoring unit is malfunctioning or functioning incorrectly, the monitoring unit may unnecessarily consume the power of the assembled battery and sufficient power of the assembled battery may not be supplied to electrical loads other than the monitoring unit, such as a vehicle inverter and the like, which may prevent the electrical loads from being driven properly. Malfunction of the dark-current mode of the monitoring unit may occur when an abnormality in a switching element or the like in the monitoring unit prevents the monitoring unit from transitioning to the dark-current mode correctly or when external noise or the like causes false triggering of the monitoring unit during the dark-current mode.
In consideration of the foregoing, it would therefore be desirable to have a battery monitoring apparatus including a monitoring unit that monitors a battery condition of an assembled battery and a control unit that controls the operation of the monitoring unit, where the control unit is capable of diagnosing whether or not a dark-current mode of the monitoring unit is functioning normally.